Patent Application
20120070814
The present invention is related to a head model that may be used for applications such as verification or adjustment for brain-imaging technologies such as PET or SPECT, and to technology for manufacturing the same.
Brain imaging is widely performed using various techniques in order to diagnose brain diseases or to study brain functions. PET (Positron Emission Tomography) or SPECT (Single Photon Emission Computed Tomography) is one example of such brain-imaging techniques. In these methods, photons (gamma rays) that are directly or indirectly generated from a radioactive drug injected into the body are detected by multiple gamma-ray detectors arranged around the head, and a brain image is formed by imaging the distribution of those photons using a computer. PET and SPECT are suitable techniques for imaging information on physiological function, such as neurotransmitter receptor distribution, glucose consumption, local blood flow, vascular reactivity and oxygen consumption, etc.
However, with PET and SPECT, there are errors based on two causes of physical errors (photon absorption and Compton scattering). Therefore, the functional images that are formed contain varying degrees of errors. So when performing an image diagnosis using PET or SPECT, it is desirable to perform verification in advance to obtain accurate results. Based on such considerations, PET and SPECT images and values obtained therefrom are verified in advance by using images obtained using subjects whose actual values are already known. For these subjects whose values are already known, human phantoms corresponding to the tissue being measured have conventionally been used.
As an example of a head model produced according to prior art that has been used for such purposes, the Hoffman 3D Phantom produced by Data Spectrum (USA) is shown in
As another example of a conventional head model, the head model disclosed in Japanese published unexamined application 2008-132021 is shown in
As described above, various head models have heretofore been proposed and used for actual verification. However, because the head model of
Moreover, a serious problem with conventional head models is that, because the head models are formed as multiple slices as shown in
Moreover, even with long hours of skilled work, it remains difficult to completely eliminate the air between the slices, and it is very difficult to obtain clean data with little noise.
The present invention has been devised with these considerations in mind, and the objective is to provide a head model that allows for the absorption coefficient of the skull to be flexibly changed and that is easy to produce.
The present invention may, for example, be embodied as a head model that may be provided for use in verification for brain imaging, where a part corresponding to the skull and a part corresponding to at least one specific region of the brain are each formed by a continuous cavity with no cuts other than an opening for liquid injection. In this head model, at least one part of the structure surrounding said cavity is composed of a material with a linear absorption coefficient equivalent to that of human soft tissue.
In other words, the present invention may be realized as a head model that may be provided for use in verification for brain imaging, comprising: a first-part for containing liquid that is provided on a part corresponding to the skull, and has a hollow structure with no discontinuous parts other than an opening for liquid injection; a second-part for containing liquid that is provided on a part corresponding to a specific region of the brain, and has a continuous hollow structure with no cuts other than an opening for liquid injection; and a structure formed as a single body so that said first and second-part for containing liquids are present therein. This structure should be formed using a material having a linear absorption coefficient equivalent to that of human soft tissue. Such a material may be selected for use from among materials having a density equivalent to that of human soft tissue, and favorable examples include acryl or ABS resin, etc.
The cavity for the part corresponding to the skull is used to include a liquid resembling bone. Then, by appropriately adjusting the type and density of the liquid, it is possible to change the γ-ray absorption coefficient arbitrarily in the skull part. In this way, not only is it possible to perform verification while taking into consideration the effects of the bone, it also becomes possible to perform verification in various states depending on the needs of the user, such as verification in states resembling bones in various states, or verification in states in which the effects of the bone are deliberately not taken into consideration.
Furthermore, by selecting transparent materials for the structure and the liquid being filled, it becomes possible to observe the inside of the phantom, it is easy to confirm whether air has entered the phantom, and, furthermore, if air has entered, it is easy to remove that air. This is a highly excellent property that has not been available in head phantoms that have been proposed in the past.
Moreover, in the head model described above, the part corresponding to the skull and the part corresponding to at least one specific region of the brain are each formed as a single hollow structure with no cuts, no discontinuous parts other than an opening for liquid injection. In other words, unlike conventional head models, the brain region is not segmented by a sliced structure, and is not discontinuous. Due to these characteristics, the problem seen in the prior art of air remaining between the slices does not occur in principle according to the head model described above. Because the cavity is a continuous structure with no cuts, even if air enters a minute structure of the brain, the air can be easily guided to the liquid-injection hole and discharged by appropriately rotating the model. In this way, according to the head model of the present invention, operations for discharging air remaining from the injection of test solution is made significantly easier compared to previous models. Consequently, it becomes possible to prepare a good model with no air remaining inside in a short period. Moreover, it becomes possible to reduce the amount of irradiation to which operators are exposed.
Consequently, the head model according to the present invention provides very excellent advantages, such as the possibility of easier preparation compared to the use of conventional head models, and the fact that more accurate verification can be performed easily.
The head model described above according to the present invention may be manufactured using, for example, stereolithography. From this perspective, the present invention may be embodied as a method for producing, for example, a head model that may be provided for use in verification for brain imaging, comprising forming, based on morphological images such as MRI images of the human head, three-dimensional CAD data representing at least each of the skull and a specific region of the brain as a hollow structure with no discontinuous parts other than an opening for liquid injection; and hardening, based on the formed three-dimensional CAD data, photo-curable resin through stereolithography.
Moreover, the present invention may, for example, be embodied as three-dimensional CAD data that, by being input into a stereolithography machine, enables a stereolithography machine to mold a head model that may be provided for use in verification for brain imaging, where the three-dimensional CAD data represent, in the head model, a part corresponding to the skull and a part corresponding to at least one specific region of the brain, respectively, as hollow structures with no discontinuous parts other than an opening for liquid injection.
Other characteristic structures and advantages included within the scope of the present invention are articulated by the following detailed descriptions and attached drawings.
The structure 302 may be composed of, for example, acryl or ABS resin. The external appearance of the structure 302 is arbitrary, but as shown in
In the head model 300, the cavities 304 and 306 are provided with openings 304a and 306a respectively for injecting liquid at their respective upper parts. But except these openings, the cavities 304 and 306 are each formed as continuous, single cavities. In other words, unlike the brain regions of the conventional head models shown in
In the cross-sectional view of
And at the same time, the cavity 304 and the cavity 306 are each independent cavities and are not mutually connected. Consequently, in principle, it is not possible for liquid that has filled the cavity 304 to be transferred to the cavity 306, or vice versa.
In the present embodiment, the shape of the cavity 304 resembles the shape of the part of the skull which houses the cerebrum and the cerebellum. This is because the purpose of use of the head model 300 is the verification of head PET images and head SPECT images, and it is sufficient as long as the effects of the skull on brain imaging performed by these devices can be examined. However, depending on the embodiment, the cavity 306 may of course be formed as a cavity resembling more skull structures.
In the present embodiment, the opening 304a for injecting liquid into the cavity 304 is provided in a circular shape on the crown of the head, and it is intended that the cavity 304 is to be sealed by inserting an appropriate cover therein. The state of the opening 304a would likely be easier to understand by looking at
By filling the cavity 304 with a liquid having an appropriate absorption coefficient, it is possible to simulate the effects of the bone during brain imaging. Examples of such a liquid include K2HPO4 solution. By changing the concentration of K2HPO4 of the solution, it is possible to arbitrarily change the absorption coefficient and perform imaging. For this reason, it becomes possible to minutely examine the effects of bones of various states on imaging. For example, it is known that bone density undergoes various changes based on age and gender. Therefore, by filling a K2HPO4 solution having an absorption coefficient corresponding to the age or gender of an expected subject, it becomes possible to perform more accurate verification.
Moreover, because the K2HPO4 solution is a transparent liquid, if a transparent material is used for the material of the head model, it is possible to visually confirm the inside of the head model. In this way, it is possible to easily visually confirm that the cavities 304, 306 are completely filled with liquid (i.e., that there is no air to impede measurement within the cavities). Furthermore, by filling the cavity 304 with a liquid having an absorption coefficient equivalent to that of soft tissue (e.g., water), it is also possible to simulate cases in which the effects of the bones are not taken into consideration.
In the above example, K2HPO4 solution was used as an example of the liquid resembling the bone, but the embodiments of the present invention are not limited to this. It is possible to appropriately select a suitable liquid that can reproduce absorption characteristics similar to those of bone and use it in a similar manner as described above.
Furthermore, depending on the purpose of use, after the absorption coefficient of the liquid filled in the cavity 304 has once been determined, the frequency at which this liquid is replaced is likely to be low. In such a case, vendors of the head model 300 may be able to sell products in which the cavity 304 has been filled with a liquid resembling the bone.
In the present embodiment, the shape of the cavity 306 has a shape resembling the gray-matter area of the brain. Consequently, by filling the cavity 306 with an appropriate radioactive drug, it is possible to reproduce a PET or SPECT image in which the drug is distributed mainly in the gray-matter area. Of course, the shape of the cavity 306 is not limited to that of the gray-matter area, and the cavity 306 may be formed as a cavity resembling the shapes of various areas depending on the objective. In addition to gray matter, examples of such areas include white matter, the cerebral neocortex, the cerebral paleocortex, the cerebrum, the midbrain, the cerebellum, the diencephalon, the nucleus basalis, the hippocampus, the cingulate gyrus, the frontal lobe, the parietal lobe, the temporal lobe, the occipital lobe, and sections of the brain atlas such as Brodmann areas, and such areas are appropriately selected according to the purpose of use of the head model.
In
In the example shown in
As described above, the cavities 304 and 306 are formed as three-dimensionally continuous cavities with no cuts other than a liquid-injection hole. Consequently, even if air remains within the cavity during the injection of liquid, the remaining air can be easily guided toward the liquid-injection hole by appropriately rotating the head model 300. After guiding the remaining air to the liquid-injection hole, the remaining air can be easily discharged by opening the spigot of the liquid-injection hole and adding an amount of liquid equivalent to the remaining air. By repeating this operation several times, it is possible to discharge almost all of the air remaining from liquid injection. In the cases of the conventional models of
As described above, in the head model 300, in order to make it easy to visually confirm the remaining air when filling in the liquid, the structure 302 is preferably made with a transparent material.
In the above head model 300, which is an embodiment, only one cavity resembling the gray matter is provided as the cavity resembling the brain region, but the embodiments of the present invention are not limited to this. Any number of cavities resembling the brain region may be provided. For example, an embodiment may be given a structure that is selected according to the type of functional image being verified using the head model, and resembles a shape formed by combining multiple regions. As an example,
As in the head model 300 described above, the head model 400 that is the embodiment shown in
In order to adjust the quantity of the drug distributing in each region, a columnar or reticular structure may be provided in the cavities. Such embodiments are shown in
The following example outlines the porosity of each region in this example, together with the type of brain function image being verified.
(A) If the functional image being verified is a SPECT image of cerebral blood flow:
Gray matter:Striatum:White matter=4:4:1
(B) In cases of dopamine transporter imaging
Gray matter:White matter:Striatum:Cerebellum=1:1:10:1
Moreover, it is also possible to arrange the above columnar body with an arbitrary density at the region where an involved area is expected to be, and prepare an arbitrary disease model.
It should be noted that if a columnar structure is provided in a cavity, it is preferable to face the direction of the columns in a substantively axial direction as shown in
In this example, first, a morphological image of an actual human, such as a head MRI, is obtained, and multiple continuous cross-sectional images are obtained (step 802). The photographs of
The modeled head-structure data are a collection of a series of cross-sectional images, but in step 808, these data are sequentially superimposed on each other before undergoing a heretofore known smoothing process or interpolation process, and are converted to three-dimensional data in which each structure also extends in the axial direction. As a result of this step, each structure gains continuity in the axial direction as well, and each structure is reconfigured as data having a three-dimensional spread. In a preferred mode, for the smoothing process, a procedure in which, for example, the number of points presenting the surface of each compartment is reduced by a factor of 10 may be used. After this step, it becomes possible to form not only cross-sectional images from the head model data but also sagittal views or coronal views.
In step 810, the cross-sectional data formed in the previous step are deformed and merged with image data having the same external appearance of a head as a human. With the above steps, three-dimensional CAD data having the necessary head shape and head structures are completed. In step 812, by inputting these three-dimensional CAD data into a heretofore known stereolithography machine, a desired head model is obtained through a heretofore known stereolithography process.
Stereolithography is a procedure that allows for a three-dimensional structure to be molded as a single body with no cuts by irradiating light on a liquid photo-curable resin in accordance with CAD data. As in the head model described above, even in cases in which it is necessary to form a hollow structure inside the solid structure, it is possible to mold the structure as a single body without using a procedure of secondary bonding, such as bonding or anastomosis. The fact that procedures such as bonding or anastomosis are not required prevents situations in which air is remained on joint surfaces, which results in decreasing in data quality during measurement. So this fact has the advantage of enabling the formation of high-quality images. Consequently, stereolithography may be said to be a very excellent procedure for forming the head model according to the present invention.
Regarding the characteristics of the spigot 1300, the tube part 1304 is hollow as shown in the cross-sectional views (B) and (C), and the opening thereof is covered by an elastic membrane 1306 formed by rubber, etc. The hollow part does not need to completely run through the tube part 1304, but may do so. Moreover, depending on the embodiment, a hollow part may be formed in the grip part 1302 as well, and depending on the embodiment, this hollow part may run through the grip part 1302 as well and form an opening above the grip part 1302. The important feature is that the surface of the basilar part of the tube part 1304 that faces the inside of the cavity is formed by the elastic membrane 1306.
When the spigot 1300 is inserted into the liquid-injection hole of the cavity of the head model, the liquid filled into the cavity faces pressure proportionate to the inserted volume of the tube part 1304. This pressure may prevent the insertion of the tube part 1304 or cause damage to the head model. However, as shown in (C), the spigot 1300 is configured so that the elastic membrane 1306 is deformed by pressure and can swell toward the interior of the hollow tube 1304. As a result of this deformation of the elastic membrane 1306, it is possible to release the pressure applied on the liquid, and it is therefore possible to smoothly insert the tube part 1304 into the cavity and prevent damage to the head model caused by liquid pressure.
The spigot 1400 has a through-hole 1406 that passes through the grip part 1402 and the tube part 1404 and opens at the top and bottom.
When the spigot 1400 is inserted into the liquid-injection hole of the cavity of the head model, the liquid filled into the cavity faces pressure proportionate to the volume of the tube part 1404. However, in the spigot 1400, because of the presence of the through-hole 1406, the liquid being pressed by the pressure may be discharged outside through the through-hole 1406. For this reason, it is possible to insert the tube part 1404 into the cavity without being obstructed by liquid pressure, and it is also possible to prevent damage to the head model caused by liquid pressure. After completely engaging the spigot 1400 in the liquid-injection hole, by sealing the top opening of the through-hole 1406 with a small spigot 1408, which is possible to completely seal the cavity.
Because the only purpose of the through-hole 1406 is to allow liquid pressed by pressure to escape, a narrow hole is sufficient, and narrowness is preferable for the purpose of sealing. When inserting the spigot 1408 into the hole 1406, the liquid naturally faces pressure proportionate to the seal tube of the spigot 1408. But by making the hole 1406 sufficiently narrow and designing the seal tube of the spigot 1408 with a small diameter, the pressure applied during insertion can be minimized, and consequently, it is possible to prevent the application of pressure that may cause damage to the head model.
Furthermore, although the spigot 1300 shown in
Using
The through-hole 1506 is fitted with another spigot 1510 like the one shown in
When the spigot 1500 is inserted into a liquid-injection hole of a cavity of a head model, as with the spigot 1300 of the previously described example, pressure is applied to the elastic membrane 1508 due to the volume of the inserted tube part 1504, and the elastic membrane 1508 deforms by swelling outwardly (
Preferred embodiments of the present invention have been described in detail above. But it should be understood that these descriptions and drawings have been presented not with the intent of limiting the scope of the present invention, but in order to contribute to understanding of the present invention. Several of the preferred embodiments of the present invention are identified in the following Claims. But the embodiments of the present invention are not limited to those explicitly described in the Claims, Description, or the Drawings, and can take various modes without deviating from the spirit of the present invention. The present invention includes within its scope all new and beneficial configurations that may be derived from these documents, regardless of whether they have been explicitly disclosed in the Claims, Description, or the Drawings of the present application.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009096188 | Apr 2009 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/056196 | 4/6/2010 | WO | 00 | 11/30/2011 |
